Question

android 怎样更新viewholder控件位置

Answer 1

用ViewHolder，主要是进行一些性能优化，减少一些不必要的重复操作。
　　具体不分析了，直接上一份代码吧：

public class MarkerItemAdapter extends BaseAdapter
{
private Context mContext = null;
private List<MarkerItem> mMarkerData = null;

public MarkerItemAdapter(Context context, List<MarkerItem> markerItems)
{
mContext = context;
mMarkerData = markerItems;
}

public void setMarkerData(List<MarkerItem> markerItems)
{
mMarkerData = markerItems;
}

@Override
public int getCount()
{
int count = 0;
if (null != mMarkerData)
{
count = mMarkerData.size();
}
return count;
}

@Override
public MarkerItem getItem(int position)
{
MarkerItem item = null;

if (null != mMarkerData)
{
item = mMarkerData.get(position);
}

return item;
}

@Override
public long getItemId(int position)
{
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent)
{
ViewHolder viewHolder = null;
if (null == convertView)
{
viewHolder = new ViewHolder();
LayoutInflater mInflater = LayoutInflater.from(mContext);
convertView = mInflater.inflate(R.layout.item_marker_item, null);

viewHolder.name = (TextView) convertView.findViewById(R.id.name);
viewHolder.description = (TextView) convertView
.findViewById(R.id.description);
viewHolder.createTime = (TextView) convertView
.findViewById(R.id.createTime);

convertView.setTag(viewHolder);
}
else
{
viewHolder = (ViewHolder) convertView.getTag();
}

// set item values to the viewHolder:

MarkerItem markerItem = getItem(position);
if (null != markerItem)
{
viewHolder.name.setText(markerItem.getName());
viewHolder.description.setText(markerItem.getDescription());
viewHolder.createTime.setText(markerItem.getCreateDate());
}

return convertView;
}

private static class ViewHolder
{
TextView name;
TextView description;
TextView createTime;
}

}

　　其中MarkerItem是自定义的类，其中包含name，description，createTime等字段，并且有相应的get和set方法。

　　ViewHolder是一个内部类，其中包含了单个项目布局中的各个控件。
　　单个项目的布局，即R.layout.item_marker_item如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:padding="5dp">

<TextView
android:id="@+id/name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Name"
android:textSize="20sp"
android:textStyle="bold" />

<TextView
android:id="@+id/description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Description"
android:textSize="18sp" />

<TextView
android:id="@+id/createTime"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="CreateTime"
android:textSize="16sp" />

</LinearLayout>